Fuel supply control system for internal combustion engines

ABSTRACT

A fuel supply control system for internal combustion engines for controlling the fuel supply controlling electromagnetic valves on the basis of processing electric signals representing respective engine operating parameters such as engine intake manifold negative pressure and engine r.p.m., wherein the electromagnetic valves are rendered inoperative to cut the fuel supply if the engine r.p.m. is above a predetermined value and if the angular speed of the motion of the engine throttle in the direction of closing the engine throttle valve exceeds a predetermined value.

United States Patent m1 Suda FUEL SUPPLY CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES [75] Inventor:

[73] Assignee: Hitachi, Ltd., Tokyo, Japan [22] Filed: Oct. 20, 1970 [21] Appl. No.: 82,275

Seiji Suda, Hitachi, Japan [30] Foreign Application Priority Data Oct. 24, 1969 Japan ..44/847l8 [52] U.S. Cl. ..l23/32 EA, 123/97 B, 123/119 R [51] Int. Cl. ..F02b 3/00, F02d 31/00 [58] Field of Search ..l23/32 EA, 32 E,

[56] References Cited UNITED STATES PATENTS Campbell ..123/32 Pribble 123/32 Fl. P. M. DETECTION 4511 Apr. 17, 1973 2,845,910 8/1958 Pribble ..l23/32 EA 3,051,152 8/1962 Paule v...l23/32 EA 3,430,616 3/1969 Glocklek..... ....l23/32 EA 3,463,130 8/1969 Reichardt.... ....l23/32 EA 3,548,792 12/1970 Palmer 123/32 EA Primary Examiner-Laurence M. Goodridge Assistant ExaminerRonald B. Cox Att0rney-Craig, Antonelli, Stewart & Hill [5 7] ABSTRACT A fuel supply control system for internal combustion engines for controlling the fuel supply controlling electromagnetic valves on the basis of processing electric signals representing respective engine operating parameters such as engine intake manifold negative pressure and engine r.p.m., wherein the electromag netic valves are rendered inoperative to cut the fuel supply if the engine rpm. is above a predetermined value and if the angular speed of the motion of the engine throttle in the direction of closing the engine throttle valve exceeds a predetermined value.

5 Claims, 4 Drawing Figures PATENTEB APR 1 H975 FIG.

FIG.

g=|e. lc

Fl G. 2

PROCESSQNG SIGNAL NEGATIVE PRESSURE DETECTION R. PM.

DETECTION INVENTOR SEIJ'I SUDA BY Antonel-LL shat-Marl.

ATTORNEYS FUEL SUPPLY CONTROL SYSTEM FOR INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION the internal combustion engine by electrically computing the duration during which fuel supply control electromagnetic valves are held operative on the basis of electric signals derived from corresponding engineoperating parameters. A typical example of the fuel supply control system, in which the exact fuel supply is computed from many engineoperating parameters, is

disclosed, for instance, in US. PatsNo. 2,980,090 (application Ser. No. 637,852, filed on Feb. 4, I957, assigned to the Bendix Corporation, patented on Apr. 18, 196i To the ends of increasing the brake-force, reducing the fuel consumption and purification of the exhaust gas, it is extremely advantageous to cut the fuel supply to the fuel supply controlled engine on an automobile or similar vehicle during the coasting of the engine. To these ends, many Venturi type carburetors and fuel injection type fuel control systems are provided with a means to cut fuel during the coasting of the engine.

.With these prior art fuel supply control systems, however, the fuel supply is cut when two conditions, that the engine throttle valve is closed and that the engine r.p.m. is detected to be above a certain value for the warming-up of the idling engine are satisfied, and it is resumed when the engine r.p.m. is reduced to the afore-said value. Therefore, with these control systems the fuel supply is not cut during the quasicoasting (during which the engine throttle valve is still not closed) and during the transition period until the closure of the throttle valve, thus reducing the effect of attaining the above ends by cutting the fuel supply that much.

SUMMARY OF THE INVENTION It is an object of theinvention to provide a fuel supply control system, in which the fuel supply is immediately cut when the coasting state of the engine is reached.

Another object of the invention is to provide a fuel supply control system, in which the resumption of the fuel supply is promptly effected at the time ofchanging of the engine's state from coasting to acceleration.

A further object of the invention is to provide for the reduction of the warming-up period of the engine by such an arrangement as to retain the fuel supply while the engine is being warmed up.

These and other objects of the invention will become more apparent from the description of the preferred embodiment ofthe invention.

The features of the invention reside in the provision of a means to control the fuel supply control electromagnetic valves in accordance with the results of electrical computation involving engine-operating parameters determining the fuel supply to the engine and a means to render inoperative the afore-said means to control the electromagnetic valves when the speed of the throttle motion in the direction of closing the throttle valve exceeds a predetermined value while the engine r.p.m. is above a predetermined value.

BRIEF DESCRIPTION OF THE DRAWING FIG. la is a plot representing engine r.p.m. with respect to time.

FIG. lb is a plot representing throttle angle with respect to time.

FIG. 1c is a fuel cut-off characteristic with respect to time.

FIG. 2 is a circuit diagram showing an embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Prior to describing a preferred embodiment of the invention, a fuel cut-off characteristic, which is conventionally attainable, will first be described in connection with FIGS. la,1 lb and 10.

It is now assumed that the engine r.p.m. N and the throttle angle 6 begin to decrease at instant I, from their initial values N and 0, as shown in FIGS. la and lb, and that the throttle angle 6 is reduced to zero (corresponding to the idling position of the throttle) at instant t The engine r.p.m. will be reduced to predetermined idling value N at a later instant t due to the mornentum. A conventional fuel supply cut-off means operates to cut fuel, at the instant 1 at which the throttle angle 0 is reduced to zero, and to resume the fuel supply at an instant t immediately before the engine reaches the r.p.m. to the predetermined idling value N as shown in FIG. lc. If the engine is being warmed up, the engine r.p.m. is increased above the predetermined normal idling speed N at the time: of reaching a Zero angle of the throttle position, so that it is necessary to preset a higher idling r.p.m. N to cut the' fuel supply when the r.p.m. is reduced to N under the warming up engine condition. This is important from the aspect of providing an increased braking force and minimizing incomplete combustion of the air-fuel mixture. It will aid in advantageously solving the exhaust gas problems. It is also important to serve the object of completing the warming-up of the engine as soon as feasible by cutting the fuel upon reaching as high an r.p.m. as possible.

With the aforementioned conventional fuel supply cutoff means, however, the fuel supply is not cut during the time interval from instant 1 till instant t during which the throttle is moving in the direction of closing the throttle valve, when decelerating the engine. ,Thus, during this time interval the engine produces output torque. Also, during this interval the engine intake manifold negative pressure is sharply reduced to reduce the amount of air admitted into the engine cylinders, resulting in excessive fuel supply to cause incomplete combustion of the air-fuell mixture. Further, in case of adjusting the idling r.p.m. N the higher idling r.p.m. should also be adjusted at the same time,

which is very inconvenient from the standpoint of maintenance.

The above drawbacks are overcome with a novel fuel supply control system according to the invention shown in FIG. 2. Referring now to FIG. 2, numeral 1 designates a signal processing means receiving the electric output signal of a negative pressure detection means 2 representing the engine manifold negative pressure, the electric output signal of an r.p.m. detection means 3 representing the r.p.m. of the engine and the electric output signal of a temperature detection means 4 representing the engine temperature. The signal processing means 1 computes the amount of fuel to be supplied from these electric signals. lts output signal is fed through resistors 5 and 6 to the base of an amplifying n-p-n transistor 7. The transistor 7 has its collector connected through a resistor 8 to a power supply lead 9 and its emitter connected through a resistor 1 1 to ground. The emitter of the transistor 7 is also connected to a control n-p-n transistor 10 having the emitter thereof connected to ground and the collector thereofconnected to a parallel circuit, which consists of parallel inductors 12, 13, 14 and 15 connected to the common supply lead 9 and in series with respective resistors 16, 17, 18 and 19 commonly connected to the emitter of the transistor 10. The inductors 12, 13, 14 and 15 are electromagnetic coils of the associated fuel injection control electromagnetic valve unit. Numeral 20 designates a constant-voltage supply lead leading from a constant-voltage control means 21 connected to the power supply lead 9. Between the lead 20 and ground is connected a monostable multi-vibrator circuit shown as enclosed within a dashed rectangle indicated at 22. The multi-vibrator circuit 22 includes two n-p-n transistors 23 and 24 having their emitters commonly connected through a resistor 25 to ground. The base of the transistor 23 is connected through a resistor 28 to the collector of the transistor 24. The base of the transistor 24 is connected through a capacitor 29 to the collector of the transistor 23. Between the lead 20 and the base of the transistor 24 is inserted a switch 31 in series with a resistor 30. The switch 31 is opened when the throttle angle is reduced to zero (upon,

reaching of the idling position of the throttle). The connection between the resistors 5 and 6 is connected to the collector of an n-p-n transistor 32, which has its emitter connected through a resistor 33 to ground and through a resistor 34 to the lead 20 and its base connected through a resistor 35 to the collector of the transistor 24 in the multi-vibrator circuit 22. The transistor 32 serves to ground the connection between the resistors 5 and 6 so as to prevent the output signal of the signal processing means 1 from being impressed on the base of the transistor 7. The output terminal of the r.p.m. detection means 3 is connected to one end of a potentiometer type resistor 36 grounded at the other end, so that a voltage proportional'to the engine r.p.m, may be applied across the resistor 36. The movable tap of the resistor 36 is connected to the base of a p-n-p transistor 37, which has its collector grounded and its emitter connected to the base of the transistor 32. Another potentiometer type resistor 38 is connected between the lead 20 and ground. lts movable terminal 39 is moved simultaneously with the engine throttle in accordance with the accelerator pedal position. It is moved in the direction of the arrow when the engine throttle is moved in the direction of opening the throttle valve. It is connected through a capacitor 40 to the cathode of a diode 41 having the anode connected to the base of the transistor 24 in the multi-vibrator circuit 22. It is also connected through a capacitor 42 to the anode of a diode 43 having the cathode connected to the base of the transistor 24. The connection between the capacitor 40 and the diode 41 is connected through a discharging resistor 44 to ground. The connection between the capacitor 42 and the diode 43 is connected through a resistor 45 to the lead 20 and through a resistor 46 to ground. The series resistors 45 and 46 constitute a voltage divider to hold the connection point between them at the emitter potential of the transistors 23 and 24 in the multi-vibrator circuit 22. The temperature detection means 4 consists of a bridge circuit connected between the lead 20 and ground. It comprises resistors 47, 48, 49, 50, and a thermistor 52 having a positive characteristic connected in parallel with the resistor 49, in a series connection of a resistor 51. The connection point 53 between the resistors 47 and 48 is connected to the base of an n-p-n transistor 54 having the emitter thereof connected through a resistor 55 to the connection point 56 between the resistors 49 and 50 and the collector thereof connected to an input terminal of the signal processing means 1. The collector of the transistor 54 is also connected to the base of a p-n-p transistor 58 having the emitter thereof connected to the lead 20 and the collector thereof connected through a resistor 59 to the base of the transistor 24 in the multi-v'ibrator circuit 2 2. The circuit parameters of the temperature detection means 4 including the series connection of the resistor 51 and the thermistor 52 are set such that the bridge circuit is electrically balanced when the engine is at temperatures requiring no warming-up, and that the transistor 54 is cut off when the balanced state of the bridge circuit is brought about.

In the operation ofthe construction described above, under normal engine-operating conditions, under which the throttle valve is open, the switch 31 is closed, so that the transistor 24in the mono-stable multi-vibrator 22 carries current, providing a low collector poten tial, and hence a low base potential of the transistor 32, to hold the transistor 32 off. In this state, the output signal of the signal processing means 1 concerning the amount of fuel to be supplied is fed through the transistor 7 to the base of the transistor 10, thus effecting the control of the fuel injection control magnetic valve unit by the energization of the electromagnetic coils l2, 13, 14 and 15.

Also in this state, the capacitors 40 and 42 connected to the movable terminal 39 of the potentiometer type resistor 38 are charged to the polarity as illustrated with respect to the movable terminal 39. If now the throttle angle 6 is changed, a voltage corresponding to the time differential of the change inthe throttle angle is developed across the resistor 44. The polarity of the voltage developed across the resistor 44, if the throttle angle is reduced, that is, if the throttle is moved in the direction of closing the throttle valve (when the movablc terminal is moving in the opposite direction to the direction of the arrow), is such as to reversely bias the base-emitter path of the transistor 24 in the multivibrator circuit 22. Thus, the circuit parameters involved may be suitably preset such that the terminal voltage developed across the resistor44 at the required angular speed of motion of the throttle in the direction of closing the throttle valve is just sufficient to cut off the transistor 24 in the multi-vibrator circuit 22. When the transistor 24 is cut off, its collector potential is increased to trigger the transistor 32, thus grounding the connection between the resistors 5 and 6. in this state, the output signal of the signal processing means 1 is not transmitted to the transistor 7, so that the fuel injection control electromagnetic valves are held closed to effect the cutting-offofthe fuel supply to the engine.

Subsequent to the exceeding of the required angular speed of motion of the throttle inthe direction of closing the throttle valve to'cut the fuel supply, if the throttle is held at an intermediate position, the switch 31 remains closed, so that the fuel supply is resumed after a quasi-stable period (t 0.7 X C29 R30), during which the transistor 24 of the mono-stable multi-vibrator circuit 22 is held off.

Even during the quasi-stable period, however, the fuel supply will be resumed if the throttle turns tomove in the direction of opening the throttle valve. At this time, the voltage on the movable terminal 39 of the potentiometer type resistor 38 increases, causing charging current to flow into the capacitor 42. The charging current passes forward throughvthe diode 43 into the base of the transistor 24 in the mono-stable multi-vibrator circuit 22 to forcibly trigger the transistor 24, thus resuming the fuel supply.

As soon as the throttle angle 0 is reduced to zero, the switch 31 is opened, so that the transistor 24 in the mono-stable multi-vibrator circuit 22 continues to be off to hold the fuel cut off. However, with decreasing engine r.p.m. N the output voltage of the r.p.m. detection means 3 decreases to decrease the voltage fed through the potentiometer type resistor 36 to the base of the transistor 37. As soon as the base voltage of the transistor 37 gets lower than the emitter potential thereof, the transistor 37 is triggered, grounding the base of the transistor 32 to cut off the transistor 32, so that the fuel supply will be resumed. Thus, by suitably setting the circuit parameters involved such that the base potential of the transistor 37 gets lower than the emitter potential thereof when the engine r.p.m. is reduced to the idling speed N the engine-operation will not be stopped.

Under the warming-up condition of the engine (under which the engine temperature is low requiring extra fuel supply), the resistor bridge circuit ofthe temperature detection means 4 is in the unbalanced state. In this state, the potential at the connection point 56 is lower than the potential at the connection point 53 since the resistance of the thermistor S2 is high, so that the emitter-base path of the transistor 54 is forwardly biased and the transistor 54 carries current. Thus, the collector potential of the transistor 54 changes with change in the engine temperature, giving the cor responding electric output signal to the signal processing means 1. Also, in the above state, base current to the transistor 58 is present and the transistor 58 carries current, giving a sufficient bias voltage to the base of the transistor 24 in the monostable multi-vibrator 22. Thus, in this state even upon reaching the required angular speed of motion of the throttle valve inthe direction of closing the throttle valve or even upon reduction of the throttle angle to zero to open the switch 31, the transistor 24 will not be cut off, so that the fuel supply will be maintained.

Under low temperature conditions, the engine operation is unstable, so that it is very advantageous to raise the heat of the engine to the stable engine temperature range as quickly as possible without interrupting the fuel supply in the above manner.

As has been described in the foregoing, according to the invention it is possible to provide a fuel supply con trol system capable of extremely effectively causing the cutting of the fuel supply to the engine.

I claim:

1. A fuel supply control system for an internal combustion engine having electro-magnetic valves for controlling the quantity of fuel supplied to the engine cylinders comprising:

a first transistor circuit, responsive to an input fuel supply signal, for controlling the activation of said valves to supply fuel to said engine;

a second transistor circuit, connected to said first transistor circuit, which, when activated, prevents said first transistor circuit from being activated by said input fuel supply signal; and

means, responsive to the engine r.p.m. being above a predetermined value and upon the rate of change of the position of the engine throttle in the direction of closing the engine throttle valve exceeding a predetermined rate, for actuating said second transistor circuit, so as to prevent said first transistor circuit from actuating said valves,

wherein said means comprises a first control circuit, coupled to said throttle, for deactivating said second transistor circuit upon the opening of said throttle, and for activating said second transistor circuit for a preselected period of time subsequent to the rate of change of position of said throttle valve, in the direction of closing the throttle valve, exceeding said predetermined rate, when said throttle remains in an intermediate position between the fully closed and fully open position thereof, and

wherein said first control circuit comprises monostable multivibrator circuit means for producing an output for said preselected period of time and having a time constant portion which determines said preselected period of time, the time constant portion of which is switchably coupled to said throttle,

having its output coupled to said second transistor circuit.

2. A fuel supply control system according to claim 1, wherein said means further comprises a second control circuit coupled between said throttle and said first control circuit, for terminating the activation of said second transistor circuit by said first control circuit upon said throttle valve being opened during said preselected period of time.

3. A fuel supply control system according to claim 2, wherein said second control circuit comprises a potentiometer providing a voltage output proportional to the degree of opening of said throttle valve and a differentiator circuit connected between the output of said potentiometer and the input of said circuit means.

4. A fuel supply control system according to claim 3, wherein said means further comprises a third transistor further comprising a temperature detector circuit connected to the input of said circuit means, for deactivating said second transistor circuit when the temperature of said engine is below a predetermined minimum. 

1. A fuel supply control system for an internal combustion engine having electro-magnetic valves for controlling the quantity of fuel supplied to the engine cylinders comprising: a first transistor circuit, responsive to an input fuel supply signal, for controlling the activation of said valves to supply fuel to said engine; a second transistor circuit, connected to said first transistor circuit, which, when activated, prevents said first transistor circuit from being activated by said input fuel supply signal; and means, responsive to the engine r.p.m. being above a predetermined value and upon the rate of change of the position of the engine throttle in the direction of closing the engine throttle valve exceeding a predetermined rate, for actuating said second transistor circuit, so as to prevent said first transistor circuit from actuating said valves, wherein said means comprises a first control circuit, coupled to said throttle, for deactivating said second transistor circuit upon the opening of said throttle, and for activating said second transistor circuit for a preselected period of time subseQuent to the rate of change of position of said throttle valve, in the direction of closing the throttle valve, exceeding said predetermined rate, when said throttle remains in an intermediate position between the fully closed and fully open position thereof, and wherein said first control circuit comprises monostable multivibrator circuit means for producing an output for said preselected period of time and having a time constant portion which determines said preselected period of time, the time constant portion of which is switchably coupled to said throttle, having its output coupled to said second transistor circuit.
 2. A fuel supply control system according to claim 1, wherein said means further comprises a second control circuit coupled between said throttle and said first control circuit, for terminating the activation of said second transistor circuit by said first control circuit upon said throttle valve being opened during said preselected period of time.
 3. A fuel supply control system according to claim 2, wherein said second control circuit comprises a potentiometer providing a voltage output proportional to the degree of opening of said throttle valve and a differentiator circuit connected between the output of said potentiometer and the input of said circuit means.
 4. A fuel supply control system according to claim 3, wherein said means further comprises a third transistor circuit responsive to a signal corresponding to the engine r.p.m. for ensuring the deactivation of said second transistor circuit upon said engine r.p.m. falling below a preset r.p.m.
 5. A fuel supply control system according to claim 4, further comprising a temperature detector circuit connected to the input of said circuit means, for deactivating said second transistor circuit when the temperature of said engine is below a predetermined minimum. 